Visible-Light-Induced Self-Cleaning Property of Bi₂Ti₂O₇‑TiO₂ Composite Nanowire Arrays

Bi₂Ti₂O₇-TiO₂ composite nanowire arrays were prepared via a two-step sequential solvothermal and subsequent calcination process. The morphology and structure of the Bi₂Ti₂O₇-TiO₂ composite nanowire array composite were characterized by X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. The UV–visible diffuse reflectance spectroscopy analysis indicated that the absorption spectrum of the Bi₂Ti₂O₇-TiO₂ composite nanowire array composite was extended to the visible-light region due to the existence of Bi₂Ti₂O₇. The Bi₂Ti₂O₇-TiO₂ composite nanowire arrays exhibit superhydrophilicity with water contact angles of 0° after irradiation with visible light, and the superhydrophilic nature is retained for at least 15 days. This effect enables us to consider self-cleaning applications that do not require permanent UV exposure. Compared to pure Bi₂Ti₂O₇ and TiO₂, the vertically aligned Bi₂Ti₂O₇-TiO₂ composite nanowire arrays showed more significant visible-light self-cleaning performance due to the synergistic effect of superhydrophilicity and significant photocatalytic activity caused by effective electron–hole separation at the interfaces of the two semiconductors, which was confirmed by the electrochemical analysis and surface photovoltage technique

Manipulating Polyaniline Fibrous Networks by Doping Tetra-β-carboxyphthalocyanine Cobalt(II) for Remarkably Enhanced Ammonia Sensing

Manipulating the morphology and protonic acid doping of polyaniline (PANI) is significant for optimizing its NH₃-sensing. Herein, tetra-β-carboxy­phthalo­cyanine cobalt­(II) (TcPcCo) acted as the dopant and structure-directing agent simultaneously to fabricate the uniform fibrous network-like PANI (PANI-TcPcCo hybrids) by a one-step polymerization at low temperature. During the reaction process, the protonic acid groups in TcPcCo not only induced the aniline monomers polymerizing into one-dimensional nanofibers (consist of both solid and hollow cylinders) with abundant tiny protuberances on the surface but also successfully doped into PANI. The resulting PANI-TcPcCo hybrids displayed the enhancement in terms of the good conductivity, the large gas adsorption capacity, and the unobstructed channels for the electron and gas transport. The central metal atoms of TcPcCo present the strong and selective affinity to NH₃. Meanwhile, the deep-seated conversion of PANI’s molecular structure after exposure in NH₃ could occur due to the presence of TcPcCo. Thus, the PANI-2.5TcPcCo sensor showed the excellent NH₃-sensing performance at room temperature, including an ultrahigh and fast response (802.7% and ∼17.0 s for 100 ppm of NH₃), a very low detection limit of 10 ppb (about 5000 parts of human olfaction limit of detection, 55 ppm), and superior NH₃-sensing stability and selectivity. The strategy developed here provides a reliable and valid way to synthesize functional PANI-based hybrids with unique morphology and appropriate doping, which are able to be extended to other areas

Hierarchical Core–Shell Carbon Nanofiber@ZnIn₂S₄ Composites for Enhanced Hydrogen Evolution Performance

Improvement of hydrogen evolution ability is an urgent task for developing advanced catalysts. As one of the promising visible-light photocatalysts, ZnIn₂S₄ suffers from the ultrafast recombination of photoinduced charges, which limits its practical application for efficient solar water splitting. Herein, we reported a two-step method to prepare hierarchical core–shell carbon nanofiber@​ZnIn₂S₄ composites. One-dimensional carbon nanofibers were first prepared by electrospinning and carbonization in N₂. The subsequent solvothermal process led to the in situ growth of ZnIn₂S₄ nanosheets on the carbon nanofibers to fabricate hierarchical structure composites. The hierarchical core–shell configuration structure can help to form an intimate contact between the ZnIn₂S₄ nanosheet shell and the carbon nanofiber backbone compared with the equivalent physical mixture and can facilitate the interfacial charge transfer driven by the excitation of ZnIn₂S₄ under visible-light irradiation. Meanwhile, the ultrathin ZnIn₂S₄ nanosheets were uniformly grown on the surface of the carbon nanofibers, which can avoid agglomeration of ZnIn₂S₄. These synergistic effects made this unique hierarchical structure composite exhibit a significantly higher visible-light photocatalytic activity toward hydrogen evolution reaction compared with pure ZnIn₂S₄ or a physical mixture of ZnIn₂S₄ and carbon nanofibers in the absence of noble metal cocatalysts

<i>In Situ</i> Carbon-Coated Yolk–Shell V₂O₃ Microspheres for Lithium-Ion Batteries

Metal oxide-based materials with yolk–shell morphology have been intensively investigated as important anodes for Li-ion batteries due to their large ion storage ability, high safety, and excellent cycling stability. In this work, <i>in situ</i> carbon-coated yolk–shell V₂O₃ microspheres were synthesized via a template-free polyol solvothermal method. The growth of yolk–shell microspheres underwent coordination and polymerization, followed by an inside–out Ostwald-ripening process and further calcination in N₂ atmosphere. The thin amorphous carbon layers coating on the microspheres’ surface came from polyol frameworks which could protect V₂O₃ during the charge–discharge process and led to a better stability in Li-ion batteries. The <i>in situ</i> carbon-coated yolk–shell V₂O₃ microspheres showed a capacity of 437.5 mAh·g^–1 after 100 cycles at a current density of 0.1 A·g^–1, which was 92.6% of its initial capability (472.5 mAh·g^–1). They were regarded as excellent electrode materials for lithium-ion batteries and exhibit good electrochemistry performance and stability